Selective-translation system



Patented Dec. 25, 1928.

' UNITED STATES PAT ENT OFFICE.

JOHN PETER SGHAFER, OF RICHMOND HILL, NEW YORK, ASSIGNOR TO WESTERN IELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y; A CORPORATION OF NEWYORK.

SELECTIVE-TRANSLATION sYsT iiu.

Application filed December 22, 1923. Serial No. 682,180,

This invention relates to selective translation systems.

One object of the invention is to selectively control the transmissionof waves through a circuit.

Another object of this invention is to receive electric wave energy andto selectively transmit this energy to a receiving device.

Another object of the invention is to eliminate interference betweenenergy of different frequencies impressed upon "a receiving circuit.

Afurther obj ectof the invention is to selec tively receive energy of aplurality of frequencies representing different signals.

An additional object of the invention is to provide a duplex radiantenergy signaling system employing a single antenna for reception andtransmission of signal waves.

A feature of the invention concerns a vacuum tube amplifier providedwith a resonant circuit connected between its input and output circuitsforeliminating current of a given frequency from said output circuit.

Another feature of the invention relates to means in the output circuitof a space discharge amplifier to prevent the flow of current of a givenfrequency through said circuit.

A further feature relates to a duplex radio transmission system havingmeans to substantially prevent any energy of the transmitted frequencyfrom reaching the local 'ev ceiving device.

A still further feature relates to resonant circuits connected with theinput and output circuits of a space discharge amplifier to excludecurrent of a particular frequency and y i a particularharmonic of thisfrequency from the output circuit;

A form of this invention which has been chosen for the purpose ofillustration com prises a radio transmitting and receiving system. Atransmitting and receiving circuit are coupled to an antenna, thereceiving 011* cuit being arranged to receive messages withoutinterference from the transmitted waves. The receivingcircuitcomprisesaspace discharge amplifier provided with a tuned cirjcuitcoupledbetweenits input and output circuits and another tuned circuit connected inshunt to its output circuit. These tuned circuits function "to excludeenergy of the een y ran mitted fr m ewes rcuit of the amplifier and alsocertain harmonies thereof. Thus signal waves are transmitted to a receving device coupled to the amplifier output circuitgvithout disturbancefrom extraneous waves.

Anequation based upon the constants of the thermionic tube and theconnected circuits is employed to determine the values of the constantsof the resonant circuit to be connected between the input and outputcircuits;

The drawing represents the terminal circuit of a duplex radiotransmission system or the terminal of atwochannel receiving circuitincluding thefeatures of this invention.

Referring to the drawing, an aerial 10 is connected to ground'through aseriescircuit comprising variable condenser 11 and Winding 12 of a highfrequency transformer 13. Block 15 represents any desiredform of radiotransmitting system or it may represent a receiving circuit which is aduplicate of that about to be described in detail. Primary winding 14 oftransformer 15 is connected to the transmitting system 15 for couplingit to the antenna 10.

The receiving system comprises an amplifier 20 comprising threeelectrode space dis charge tubes 21 having an input circuit 22 and aload circuit 23. The circuit 22 is connected to the grid and filamentoftube 21 and includes a grid polarizing battery 24 in series withresonant circuit 26,127,which is preferably tuned to the frequency ofwaves that it is desired to receive. The inductance 26 constitutes awinding of the transformer 13 whereby the amplifier20 is coupled totheantenna 10. By means of the variable concuit is made possible.

denser 27 the tuning of the resonant cir- Load circuit 23 is connectedto the plate form of detector or den'iodulator having a signal receiverconnected thereto. The receiver 35 may be immediate to the amplifier 20or at the end of atransmission line.

A resonant circuit l0 which is connected between the input and outputcircuits of the amplifier 20 comprises an inductance 37, a condenser 38and an adjustable resistance 39.

Inductance 41 in series with variable condenser 42 constitutes a seriesresonant circuit connected in shunt to the load circuit 23.

In an article by H. N. Nichols in the Physical Review, Lancaster, Pil N.S. Vol. XIII, 6, June 19, 1919, page 4:04, it is shown that a vacuumtube such as tube 21 connected in a circuit such as shown in the drawingmay be considered as a virtual source of alternating electromotiveforce. However, in the drawing, amplifier 20 may be considered to havetwo alternating current generators, connected in series throughassociated alternating current resistances. For example, resonantcircuit 26, 27 supplies an electromotive force acting through theimpedance of resonant circuit 40; tube 21 supplies a virtual alternatingelectromotive force which acts through the internal alternating currentresistance of tube 21. In addition the electromotive force of tube 21 is180 out of phase with the electromotive force produced by resonantcircuit 26, 27. It has, furthermore, been shown that an alternatingcurrent of a given frequency,produced by on electromotive force in theresonant circuit 26, 27 may be excluded from the load circut 23. Byreferring to the drawing it is seen that the circuit 23 is connectedbetween the junction points connecting one of these alternating currentgenerators with its associated impedance to the other alternatingcurrent generator and its associated impedance. Energy of this frequencyis excluded from the load circuit 23 by tuning resonantcircuit 10 toresonance at the frequency which it is desired to exclude and by furtheradjusting the resistance 39 to a valuehaving that relation to the valueof the alternating current resistance of tube 21, which is explainedmore fully later. When the resistance 39 is adjusted to the proper valueand when resonant circuit -10 is tuned to the frequency tobe excluded,variations in the electromotire force of this frequency supplied byresonant circuit 26, 27 will not produce any variation of this frequencyin the current in circuit 23.

Any reactance which may exist between the plate and grid of tube 21maybe compensated for in the tuning of resonant circuit 40 so that thearallel paths comprising this reactance and the impedance of resonantcircuit 40 will form a resonant circuit for the frequency to be excludedfrom the output circuit.

As shown in the article referred to above, it has been found thatthefollowing equation applies to the circuit shown in Fig. 1 where trepresents the amplification constant of the tube 21, I the currentflowing in the output circuit 28 in response to the alternatingpotential e, and R the alternating current resistance between thecathode and anode of the In the above equation Z, represents theimpedance of resonant circuit 40, Z represents the impedance of loadcircuit 23. By adjust ing the resistance 39 of the impedance Z,,, at afrequency corresponding to zero rcactance of the impedance Z, inaccordance with the equation: R

where 1' represents the resistance 39, it will be seen that thenumerator of the second member of the equation (I) becomes zero, or inother words the current I in the output circuit of the amplifier will bezero for the freuency at which Z is equal to 1'. If 1' is adusted tovalues other than in accordance with equation (2), above, the magnitudeof the output current of the frequency at which Z, is of zero reactancemay be varied to any desired value. y

In the operation of this system, wave energy of a frequency representedby f, is transmitted from the system indi-ntcd by block 15 to theantenna 10 from which it is radiated. In the alternative arrangement inwhich the circuit 15 is a receiving circuit energy of this samefrequency may be received by the antenna 10 and transmitted to thesystem 15. The receiving device 35 is arranged to receive energy offrequency rcprcsented by f.,. Energy of the frequency f, is necessarilyimpressed on the input cir' cuit of tube 21 but by adjusting resonantcircuit 40 in accordance with the method al ready described, the energyof the frequency 7, may be excluded from the load circuit 23 andconsequently from the receiving device 35. It is found, however, thatunder certain conditions, energy having a frequency which is a harmonicof the frequency f, may be transmitted to the output circuit through theamplifier and to exclude energy of this harmonic frequency from loadcircuit 23, a resonant circuit 41, 42 is providedin shunt thereto. Bymeans of variable condenser 42, this resonant circuit is adjusted toresonance at the harmonic frequencywhich it is desired to exclude. Thiscircuit then comprises a path of low impedance to the harmonic frequencywhereby the latter is prevented from flowing through the load circuit23. It will in general be desirable to tune resonant circuit t1, (2 tothe frequency of the second harmonic. The resonance circuit 41, e2offers high impedance to waves of the frequency which it is desired toreceive and consequently llU lit

they are transmitted through the load circuit to receiving device 35.

Although this invention has been described in connection with a specificembodiment, it is not intended that its scope should be limited thereto.

What is claimed is:

1. In an electric: circuit, a relay device having input and outputcircuits, an impedance element connected between said circuits toprevent the flow of waves of given frequency through said outputcircuit, and ah impedance element connected to said output circuit toprevent the flow of waves harmonic to said given frequency in saidoutput circuit.

2. In a radiant energy transmission system, means for generating wavesof frequency f means for impressing waves of said frequency upon anantenna, means for receiving energy of frequency f, coupled to saidantenna, said last named means comprising a space discharge amplifierhaving input and output circuits, means coupled to said circuits toexclude energy of frequency f, from said output circuit, and aseriesresonant circuit in shunt to said output circuit, said resonant circuitbeing tuned to the frequency 2 3. In combination, a space dischargeamplitier having input and output circuits, a resonant circuit connectedbetween said input and output circuits, and a resonant circuit in saidoutput circuit to supply low impedance paths to energy of a givenfrequency and the second harmonic thereof respectively whereby energy ofthese frequency is ex cluded from said output circuit.

4. In combination, an amplifier having an input circuit and an outputcircuit, means connected between said circuits to selectively preventthe transmission through said output circuit of waves of a givenfrequency, and means in shunt to said output circuit of substantiallyZero impedance to waves of twice said given frequency but of highimpedance to waves of other frequencies.

5. In a radiant energy transmission system,

a receiving system and a transmitting system coupled to a commonantenna, a space discharge amplifier in one of said system having inputand output circuits, adjustable means connected between said circuits toexclude energy of the frequency produced by said transmitting systemfrom said output circuit, and means of substantially zero impedance towaves having a frequency harmonic to that of Waves from saidtransmitting system but of high impedance to waves of other frequenciesconnected across'said output circuit.

6. In a duplex transmission system, an antenna, a transmitting systemand a selective receiving system coupled to said antenna, said receivingsystem comprising an amplifier having input and output circuits, and aresonant circuit connected in shunt to said output circuit and a secondresonant circuit connectedvbetweenr said input and output circuits, saidresonant circuits being tuned to the frequency assigned to saidtransmitting system and a given harmonic thereof, whereby saidfrequencies are prevented from flowing in an output circuit of saidamplifier.

7. In a signaling system, a receiving conductor, a pluralit of circuitscoupled to said conductor, said circuits having predeterminedassignmentof carrier frequencies,

and a plurality of resonant circuits associated with one of saidcircuits to preventiit terference from waves of the carrier frequencyassigned to another circuit and a given harmonic thereof. i 8. In anelectric circuit a relay device having input and output paths, a, tunedcircuit 7 connected between said paths to prevent the transmission ofwaves of a given frequency to said output path, and a second tunedcircuit connected in said output path to prevent the flow of anothergiven frequency therein, one of said given frequencies being a harmonicof the other.

In witness whereof,vI hereunto subscribe my name this 19 day ofDecember, A. D. 1923.

J. PETER SCHAFER.

